The present invention generally relates to intravascular medical devices and methods for sensing and monitoring fluid pressure. More specifically, the present invention relates to intravascular diagnostic devices that consist of hollow tubes or wires used to sense and monitor intravascular fluid pressure. Still more specifically, the present invention relates to the improvement of stiffness or torquability of such devices. Those skilled in the art will recognize the benefits of applying the present invention to similar fields not discussed herein.
Angioplasty procedures have gained wide acceptance in recent years as efficient and effective methods for treating many types of vascular disease. In particular, angioplasty is widely used for opening stenosis or occlusions in the coronary arteries, although it is also used for the treatment of stenosis in other parts of the vascular system.
The most widely used form of angioplasty makes use of a dilation catheter which has an inflatable balloon at its distal end. Inflation of the balloon at the site of the occlusion causes a widening of the vessel to reestablish an acceptable blood flow through the vessel.
It often is desirable to determine the severity of the occlusion in order to properly choose a dilation catheter or to make a determination as to whether treatment is required at all. Various techniques have been used to determine the severity of the occlusion. One way of determining the severity of the occlusion is to measure pressure at points both proximal to and distal of the occlusion.
Devices that are used for this purpose include catheter-like members with some type of pressure-sensing device incorporated therein. Such devices often referred to a pressure-sensing guidewire since they can provide the dual function of guidewire and a pressure measuring device. One known device measures the pressure as a function of the deflection of a diaphragm located at the proximal end of the catheter. Examples of intravascular pressure-sensing guidewires are illustrated in U.S. Pat. Nos. 5,873,835 and 5,836,835.
One problem associated with currently available pressure-sensing devices is the reduced function as a guidewire. Specifically, because the catheters or elongated tubes are hollow, they bend easily and are often difficult to maneuver, steer or control.
Accordingly, there is a need for an improved device which can function both as a pressure-sensing device and a guidewire with improved controllability. Still further, there is a need for an improved intravascular pressure-sensing device which can also serve as a guidewire but which has improved torque or stiffness without compromising the pressure-sensing capabilities of the device.
The present invention overcomes the deficiencies of the prior art by providing a pressure-sensing guidewire assembly that comprises an elongated tubular member having a lumen extending through the member. The elongated tubular member further comprises an outer surface and an inner surface and at least one opening extending between the inner and outer surfaces and providing communication between the outer surface and the lumen. Pressure is communicated from the vascular environment outside of the lumen, through the opening and down the lumen to a transducer device connected to a proximal end of the elongated tubular member. In order to improve the performance of the pressure-sensing guidewire assembly to function as a guidewire, a torque enhancing mandrel is inserted into the lumen during the insertion of the assembly through a vessel or artery and the positioning of the assembly at the place of interest in the vascular system. To take a pressure measurement, the torque enhancing member is removed from the elongated tubular member and a pressure reading device such as a transducer is connected to a proximal end of the tubular member. Either the proximal or distal ends of the torque enhancing member and tubular member are detachably connected together.
In another embodiment, a method for increasing the stiffness or torquability of a pressure measuring device is provided which comprises providing an elongated tubular member having a lumen extending through the elongated tubular member. The elongated tubular member being a pressure-sensing guidewire. The method including the step of inserting a torque enhancing mandrel into the lumen and detachably connecting the torque enhancing member to the elongated tubular member to provide increased stiffness and torquability to the pressure-sensing guidewire.